As a measure for expanding the coverage of a cellular communication system, the introduction of femto base stations that form cells for covering narrow areas such as residential houses, schools, and enterprises has proceeded. Further, expectation for local IP access services to be connected to local networks utilized through femto base stations managed by homes, schools, enterprises and the like has increased. This is expectation for the high level of QoS guarantee and security according to the use of cellular technology, as compared to local network connection using a wireless LAN in the related art.
The local network connection through the femto base station has been studied in standard-setting organizations that formulate cellular standard technology. Particularly, in 3GPP (3rd Generation Partnership Project), as local IP access (LIPA), the formulation of network architecture, procedures, and protocols have proceeded (Non Patent Literature 1).
Non Patent Literature 1 discloses a method of causing a mobile terminal to specify an access point name (hereinafter, referred to as an APN) as an identifier indicating a local network (hereinafter, also referred to as a LIPA network) serving as a connection destination and performing local IP access (LIPA).
Here, a use case (remote access to a local network; hereinafter, also referred to as Remote IP Access or RIPA) is considered in which secure connection to a local network is performed from the outside of home, schools, or enterprises using a femto base station.
The femto base station installed in home is connected to a core network of an operator through a broadband channel. When a cable for connection to the broadband channel is detached, the femto base station is connected to a neighboring macro base station through a cellular channel to establish connection to a core network, and maintains the connection of the mobile terminal located down the femto base station. In this manner, technology for expanding the coverage of a cellular communication system using the cellular channel is particularly called relay technology (or mobile relay technology). The relay technology in 3GPP has been examined in TR36.806.
As mentioned above, when the mobile terminal accommodated in a moving femto base station (hereinafter, referred to as the mobile base station) moves together with the mobile base station, the movement thereof in the cellular system is hidden. That is, when seen from the mobile terminal, the high-position base station does not change and thus the movement is not detected. Therefore, a mobility management process (Tracking Update Procedure specified in TS23.401, Location Update Procedure specified in TS23.060, or the like) or a handover process is not performed. Thereby, when the mobile base station accommodates a plurality of mobile terminals, it is characterized by being capable of reducing mobility management signaling from individual mobile terminals, and reducing traffic costs. However, as previously stated, the connection to a local network is performed by the explicit specification of the mobile terminal, and it is assumed that the switching of the LIPA and RIPA is also performed by the reconnection of the mobile terminal or a handover process.
Based on these factors, in an environment in which the mobile base station accommodates the mobile terminal, the mobile terminal cannot detect its own movement, and thus there is a problem in that the connection to the local network cannot be correctly switched at the time of the movement associated with the mobile base station. That is, there is a problem in that the movement along with the mobile base station causes a communication session to be cut off unexpectedly, and user convenience is considerably damaged. In order to solve such problems, a method of causing the mobile base station to establish a secure tunnel such as a home gateway and a VPN (Virtual Private Network) at home, and collectively accommodating the local network connection of the mobile terminal located down the mobile base station is considered.